Developmental disabilities (DD) research has depended on volunteer and clinical samples, with limited racial/ethnic diversity. This study focused on improving diversity and retention in DD research. The sample included 225 parents with a child with DD and 4,002 parents without children with DD from diverse racial/ethnic groups, drawn from Midlife in the United States, a national longitudinal study. Unexpectedly, parents of children with DD from diverse racial/ethnic groups were more likely to participate longitudinally than other groups. Relative participant payment was a factor that enhanced their likelihood of retention. This research illustrates how large national studies can be leveraged to increase representativeness and ongoing participation of diverse racial/ethnic groups, especially in combination with other factors, such as parenting a child with DD.